Tuesday, 20 October 2015

Whimsical cartoonist plants wonky desert cypress

Yesterday, cartoonist and poet Michael Leunig planted a tree in our Melbourne Gardens. At first we sought a curly plant of some kind, such as one of the 'tortured' willows or hazels, but we settled in the end on a tree with just a hint of asymmetry and one that should survive Melbourne's toughening climate - the Saharan Cypress, Cupressus depreziana.

This is the second in our rebooted Commemorative Tree program, following at a safe distance behind musician Nick Cave's planting of a Henry's Lime in December last year. Michael Leunig is of course a much-loved social commentator in Melbourne and someone willing to speak his mind and hold strong opinions.

The selection of Leunig was consistent with the choice of Nick Cave, both having with a distinctive individual style and representative of creative and liberal Melbourne. His contributions to Melbourne and the world's cultural life have been over an extensive period, and a little 'outside the box'. For 46 years he has been contributing his whimsy and wit to newspapers, and in July this year he celebrated his 70th birthday. As a bonus, Leunig regularly references trees and nature in his pictures and writing.

So to the tree itself. Not really curly but it does develop a curious habit. The Saharan Cypress is, as you'd expect, a rather drought tolerant conifer. It's from the central Sahara Desert, growing above 1000 metres in the Tassili n'Ajjer Mountains, in eastern Algeria. It was brought to the attention of western scientists by Captain Duprez, commander of a French army camp stationed nearby.

There are only 233 individual plants remaining in its native habitat. So few, and they are so long-lived (the oldest dated at 2,300 years old), that each tree has its own name. These names in the local Tamashek language relate to location (the one near the flat stones, or a mountain), use (to hand things on) or perhaps an important nearby feature (pool of water at its roots).

Tamashek also provides an intriguing common name, Tarout. 'Tarout' is a butcher's term for the windpipe and attached lungs of an animal, and due to its wonky top our tree will eventually have a passing resemblance to this collection of internal organs (held windpipe-down...). Not curly, but a little off-centre perhaps. Perhaps also a nod to Leunig being the son of a slaughterman and having worked in abattoirs in his early years...

The Saharan Cypress is more common in cultivation, particularly it seems in Australia where a thicket of the Saharan Cypress and its close relative the Moroccan Cypress (sometimes considered to be a variety of Cupressus depreziana, called var. atlantica) were planted eight years ago in the National Arboretum in Canberra.

In the Algeria mountains summer maxima are around 20-30 degrees C, and winter days 1-13 degrees C. Not unlike Melbourne, although we get a little hotter in summer. Annual rainfall is variable but around an extremely low 30 mm, compared to our current 650 mm a year in Melbourne.

While we anticipate a more extreme climate in Melbourne over coming decades we don't expect rainfall to drop that much. On the other hand we are always on the look out for plants that need less water and are able to survive the occasional drought. We expect this species will do just fine in Melbourne Gardens.

And if it does, we can tell the story not only of its exotic origins and endangered status, but also of its male dominated reproduction. At least some of the time the Saharan Cypress employs what is called apomixis, where seeds develop without sexual fusion. In this particular case the important genes all come from the pollen, the male 'parent'. It seems the female 'parent' provides nutritional content for the seed but none of the genetic content that ends up in the new plant.

It's unclear if this happens all the time, or why it happens. It may be that in the small remnant population in Algiers there are no longer any viable female reproductive cells produced. Odd things can happen when you get a small number of individuals interbreeding.

The specimen Michael Leunig planted yesterday, 19 October 2015, has been doing very nicely in our nursery (modeled here next to Dermot Molloy). Its success out in the Gardens will depend on how its genes, whatever their origin, allow it to respond to our ever changing Melbourne climate.